1. Field of the Invention
The present invention relates to a wiper control apparatus using a semiconductor switching element such as a MOSFET.
2. Description of the Prior Art
One of previously known wiper control apparatus is disclosed in JP-A-9-193748. In this wiper control apparatus, as seen from FIG. 21, when a combination switch 17 is set at an intermittent mode (INT), a driving circuit 20 turns on an interruption switch MOSFET 19 to start a motor 15 so that a wiper reciprocates once. Then, the terminals P and Q of a wiper switch 16 are connected to each other. Then, the driving circuit 20 turns off the interruption switch 19 to interrupt the power supply to the motor 15. When the terminals P and Q of the wiper switch 16 are connected, a battery-voltage side terminal K and a ground side terminal J are connected to each other through a contact terminal T1 and braking resistor 18 so that the motor 15 is braked. Thus, the wiper stops quickly.
However, the wiper control apparatus presents the following problems.
(1) When the wiper motor 15 generates an abnormal current as if it is locked, a large current continues to flow through a MOSFET 19 or resistor 18. Therefore, the resistor 18 or MOSFET 19 may be excessively heated and burned. In order to avoid the burning, a countermeasure for setting a large current rating for the resistor 18 and MOSFET 19 and providing a radiator is required. This upsizes the apparatus and makes it expensive.
(2) When the plus terminal and minus terminal of a battery 11 are erroneously connected in a reverse direction, a large current continues to flow through the parasitic diode of the MOSFET 19 and the resistor 18. Therefore, the resistor 18 and the MOSFET may be burned.
(3) For some time after the MOSFET 19 turns on, since the terminals P and Q of the wiper switch 16 remain connected, a tunneling current will flow through a passage of wiper switch 16xe2x86x92resistor 18xe2x86x92MOSFET 19 from the battery 11. This leads to unnecessary dissipation of heat and noise.
(4) Setting the intermittent time and the after-wash wiping operation time after the washer has been operated is carried out in an analog manner using the charging/discharging theory of a capacitor. This leads to a large change in these times.
An object of the present invention is to solve the problem of the conventional wiper control apparatus to provide a wiper control apparatus which is compact, reliable and surely operable using a semiconductor switch and a digital controller.
In order to attain the above object, in accordance with the first aspect of the present invention, there is provided a wiper control apparatus comprising:
a combination switch for setting an operation mode of a wiper at an intermittent wiper operation mode or a continuous wiper operation mode by means of position setting;
a wiper motor which is driven according to the operation mode set by the combination switch;
an autostop (AS) switch for producing a signal having a level varying according to a park position and other positions as the wiper motor rotates;
a first semiconductor switch element for on/off controlling energization of the wiper motor;
a controller for supplying a ON/OFF control signal to the first semiconductor switch element, wherein while the wiper operates in the operation mode set by the combination switch, if the level of the signal produced from the AS switch does not vary for a longer period than a prescribed abnormality detecting period owing to occurrence of abnormality of the wiper motor, the controller forcibly turns off the first semiconductor switch element.
In this configuration, when the abnormality of the wiper motor occurs, the controller monitors the duration of the abnormality to interrupt the energization. Therefore, the semiconductor switch element is not required to be excessively upsized, and hence can be down-sized and made inexpensive. In addition, the reliability of the entire wiper control apparatus inclusive of a driving circuit and a wiper motor is improved.
Preferably, after the abnormality is released, the controller decides that a set position of the combination switch has been changed and turns on the first semiconductor switch element to operate the wiper in the operation mode corresponding to the changed position. In this configuration, by position setting after the abnormality of the wiper motor has been released, the wiper operation can be resumed in the operation mode corresponding to the selected position.
Further, preferably, the controller is supplied with a driving voltage through an ignition switch from a battery, and after the abnormality is released, the controller detects re-energization successive to xe2x80x9coffxe2x80x9d of the ignition switch to turn on the semiconductor switch element and restores the operation of the wiper which had been set when the abnormality has occurred. In this configuration, by the turn off and re-energization of the ignition switch, the wiper operation stopped owing to occurrence of the abnormality can be restored.
In accordance with the second aspect of the present invention, there is provided a wiper control apparatus comprising:
a combination switch for setting an operation mode of a wiper at an intermittent wiper operation mode or a continuous wiper operation mode by means of position selection;
a wiper motor which is driven according to the operation mode set by the combination switch;
an autostop (AS) switch for producing a signal whose level varies according to a park position and other positions as the wiper motor rotates;
a first semiconductor switch element for on/off controlling energization of the wiper motor;
a controller for supplying an ON/OFF control signal to the first semiconductor switch element, wherein when an OFF position of the combination switch is set while the wiper operates, the controller maintains the xe2x80x9cONxe2x80x9d of the first semiconductor switch element until the AS switch produces a signal having the level corresponding to the park position of the wiper. In this configuration, even when the combination switch is changed into the OFF position, the controller keeps the ON of the semiconductor switch element until the wiper returns to the park position, the wiper does not stop on the way.
In accordance with the third aspect of the present invention, there is provided a wiper control apparatus comprising:
a combination switch for setting an operation mode of a wiper at an intermittent wiper operation mode or a continuous wiper operation mode by means of position selection;
a wiper motor which is driven according to the operation mode set by the combination switch;
an autostop (AS) switch for producing a signal whose level varies according to a park position and other positions as the wiper motor rotates;
a first semiconductor switch element for on/off controlling energization of the wiper motor;
a second semiconductor switch element for turning on a closed circuit for braking the wiper motor by passing a reverse current through the wiper motor while energization of the wiper motor is off;
a controller for supplying a first ON/OFF control signal to the first semiconductor switch element and a second ON/OFF control signal to the second semiconductor switch element, wherein the controller provides a time delay td between rising edges or between trailing edges of the first control signal and the second control signal.
In this configuration, since the controller provides a time delay td between rising edges or between trailing edges of the first control signal and the second control signal, it is possible to prevent the first and second semiconductor switch elements from turning on simultaneously and a tunneling current from flowing, thus eliminating unnecessary dissipation of heat and noise.
Preferably, the first semiconductor switch element is an N-channel type MOSFET and the second semiconductor switch element is a P-type MOSFET. Therefore, these semiconductor switch elements can be down-sized and made inexpensive.
Preferably, a Zener diode is connected in series with the second semiconductor switch element. Therefore, the reverse electromotive force of the wiper motor when the first semiconductor switch element is overheated and interrupted can be dissipated. The second semiconductor switch element when it is reversed-connected owing to erroneous connection of the battery can be protected. Further, the second semiconductor switch element can be surely turned off by shifting the potential at the control electrode.
In accordance with the fourth aspect of the present invention, there is provided a wiper control apparatus comprising:
a combination switch for setting an operation mode of a wiper at an intermittent wiper operation mode, a continuous wiper operation mode or a washer operation mode by means of position selection;
a wiper motor which is driven according to the operation mode set by the combination switch;
an autostop (AS) switch for producing a signal whose level varies according to a park position and other positions as the wiper motor rotates;
a first semiconductor switch element for on/off controlling energization of the wiper motor;
a washer motor which is energized and driven by the combination switch while the wiper operates in the washer mode;
a controller for supplying an ON/OFF control signal to the first semiconductor switch element, wherein the controller controls the first semiconductor switch element to be xe2x80x9cONxe2x80x9d while the combination switch is at the washer operation mode, and keeps the xe2x80x9cONxe2x80x9d of the first semiconductor switch element until the wiper reciprocates by a prescribed number of times to perform an after-wash wiping operation after the combination switch has been changed into the OFF position.
In this configuration, the number of times of after-wash wiping can be defined precisely so that its error can be removed.
Preferably, the prescribed number of times can be variable set by the controller. Therefore, it can be set at any optional number of times.
Preferably, when the combination switch is changed from the washer operation mode into the OFF position through another mode, if the number of times of the after-wash wiping does not still reach a prescribed value, the controller keeps the xe2x80x9cONxe2x80x9d of the first semiconductor element until the wiper performs the after-wash wiping by the remaining number of times. In this configuration, even when the combination switch is changed from the ON position to the OFF position during the after-wash wiping after the wash operation has been made, the number of times of the after-wash wiping can be defined precisely so that its error can be eliminated.
In the first aspect, preferably, the combination switch includes a variable resistor for adjusting an intermittent time while it is in the intermittent wipe operation mode, and the controller includes an VR input terminal for inputting a resistance value of the variable resistor from the combination switch so that the resistance value of the variable resistor is A/D converted to set the intermittent time in a digital manner.
In this configuration, since the intermittent time can be precisely set at a prescribed time by the controller, the timing accuracy of the intermittent operation can be improved.
Preferably, the controller sets the intermittent time at a prescribed value when the VR input terminal is released. In this configuration, when the VR input terminal is released, the timing accuracy of the intermittent operation can be improved.
In accordance with the fifth aspect of the present invention, there is provided a wiper control apparatus comprising:
a combination switch for setting an operation mode of a wiper at an intermittent wiper operation mode or a continuous wiper operation mode by means of position setting;
a wiper motor which is driven according to the operation mode set by the combination switch;
an autostop (AS) switch for producing a signal whose level varies according to a park position and other positions as the wiper motor rotates;
a first semiconductor switch element for on/off controlling energization of the wiper motor; and
a controller for supplying an ON/OFF control signal to the first semiconductor switch element, wherein the first semiconductor switch element is provided with an overheating interruption/protection circuit so that it is self-interrupted by the over-heating interruption/protection circuit when it is overheated owing to occurrence of abnormality of the wiper motor.
In this configuration, before the first semiconductor switch is broken owing to its overheating, the over-heating interruption/protection circuit turns off the gate of the MOSFET 4 and stops the energization thereof. Namely, when the abnormal current continue to flow, the current is interrupted quickly so that the current rating of the first semiconductor switch is not required to be excessively large. Thus, the first semiconductor switch can be downsized and made inexpensive. The reliability of the apparatus inclusive of the driving circuit and motor can be improved.
Preferably, after the abnormality is released, the controller decides that a set position of the combination switch has been changed and turns on the first semiconductor switch element to operate the wiper in the operation mode corresponding to the selected position.
In this configuration, by changing the set position after the abnormality of the wiper motor has been released, the wiper operation can be resumed in the operation mode corresponding to the changed set position.
Preferably, the controller is supplied with a driving voltage through an ignition switch from a battery, and after the abnormality is released, the controller detects re-energization successive to xe2x80x9coffxe2x80x9d of the ignition switch to turn on the semiconductor switch element and restore the operation of the wiper which had been set when the abnormality has occurred. In this configuration, by the turn off and re-energization of the ignition switch, the wiper operation stopped owing to occurrence of the abnormality can be restored.
In the first to the fifth aspects of the invention, preferably, the first semiconductor switch element is connected to an upstream side or downstream side of the wiper motor. In this configuration, since the first semiconductor switch element may be arranged at either the downstream side or upstream side, particularly, where it is arranged on the upstream side, its protection against the failure such as shorting of a wire can be made, thereby improving the safety for the apparatus.
In the first to fifth aspects of the invention, preferably, the controller chopper-controls the ON/OFF control signal to the first semiconductor switch element so that the wiper motor is driven at variable speeds.
In this configuration, the structure of the wiper control apparatus can be simplified. By varying the duty ratio of the control signal, the speed of the wiper motor can be made variable in plural steps of three or more or continuously. Further, the chopper frequency is adjusted to avoid the resonance frequency different for a vehicle type, thereby suppressing the noise by the chopper control.
Preferably, in the fifth aspect of the invention, if the wiper has not yet been returned when the ignition switch is energized, the controller drives the wiper motor at a high speed so that the wiper is returned to the park position.
In this configuration, where the wiper remains on the windshield glass when the IG switch is energized, by returning the wiper to the park position in the high speed mode, the field of viewer can be assured swiftly.
Preferably, the wiper control apparatus according to any one of the first to fifth aspects can be employed together with a relay-type wiper control apparatus, and the controller controls the operation of both wiper control apparatus and relay-type control apparatus.
In this configuration, the controller includes the collected function of controlling both the semiconductor switch(s) and relay, and hence down-sized and made inexpensive. The control is correlated between the front wiper and rear wiper.
The above and other objects and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings.